Multiple Gestation and Anaesthesia

Quick Answer

Multiple gestations (twins, triplets, higher-order multiples) complicate 1.6% of pregnancies in Australia but account for 10-15% of perinatal mortality and morbidity. Twin pregnancies are classified as monochorionic (single placenta, 20-30%, higher risk) or dichorionic (two placentas, 70-80%, lower risk), with chorionicity determined by ultrasound at 10-14 weeks. Anaesthetic considerations include earlier planned delivery (twins 36-38 weeks, triplets 34-36 weeks), increased caesarean section rate (50-75% for twins, >90% for triplets), higher risk of postpartum haemorrhage (5-10× singleton pregnancy due to uterine atony and larger placental bed), phenylephrine as first-line vasopressor for spinal hypotension (avoid ephedrine in uteroplacental insufficiency), and preparation for massive haemorrhage (two large-bore IVs, blood crossmatch, cell salvage consideration). Twin-to-twin transfusion syndrome (TTTS) affects 10-15% of monochorionic twins, causing polyhydramnios-recipient and oligohydramnios-donor discordance with high-output cardiac failure risk. Neuraxial anaesthesia preferred if time allows; general anaesthesia for urgent/emergent deliveries with higher aspiration risk and difficult airway incidence. Indigenous women experience 1.5-2× higher multiple birth rates in some regions, compounded by limited access to tertiary-level maternal-fetal medicine, requiring coordinated care with Aboriginal health services, early referral to high-risk obstetric units, and culturally safe delivery planning.

Pathophysiology

Multiple Gestation Classification and Physiology

Classification by Zygosity:

Monozygotic Twin Chorionicity:

Physiological Changes in Multiple Gestation:

Cardiovascular Adaptations:

• Greater blood volume expansion: 50-60% increase (vs. 40-50% singletons), peaking at 28-32 weeks
• Higher cardiac output: 50-60% increase (vs. 30-40% singletons) by third trimester
• Increased stroke volume and heart rate: Greater hemodynamic reserve demands
• Lower systemic vascular resistance: More pronounced vasodilation
• Aortocaval compression: Occurs earlier and more severe due to larger uterine size
• Implications:
  • Greater hemodynamic instability with neuraxial blockade
  • Earlier onset of supine hypotensive syndrome
  • Higher risk of cardiac decompensation in labour

Respiratory Changes:

• More pronounced reduction in FRC: Greater elevation of diaphragm
• Increased oxygen consumption: Higher metabolic demands
• Earlier dyspnea: Often presents in second trimester
• Implications:
  • Faster desaturation during apnea
  • Higher respiratory reserve demands during labour
  • Earlier need for supplemental oxygen

Gastrointestinal:

• More severe gastroesophageal reflux: Larger uterus increases intra-abdominal pressure
• Delayed gastric emptying: More pronounced in multiple gestation
• Implications:
  • Higher aspiration risk
  • Earlier and more aggressive aspiration prophylaxis required
  • Lower threshold for general anaesthesia with RSI

Uteroplacental:

• Larger placental bed: Increased surface area, more vascular
• Higher risk of placenta praevia: 2-3× singleton rate
• Increased risk of abruption: Mechanical and vascular factors
• Uterine overdistension: Higher risk of atony and PPH

Twin-to-Twin Transfusion Syndrome (TTTS)

Definition: TTTS complicates 10-15% of monochorionic-diamniotic (MoDi) twin pregnancies, caused by unbalanced arteriovenous anastomoses in shared placenta.

Pathophysiology:

Vascular Anastomoses:

• Arterio-venous (AV): Deep, unidirectional — major contributor to TTTS
• Arterio-arterial (AA): Superficial, bidirectional — protective
• Veno-venous (VV): Superficial, bidirectional

Net Flow Imbalance:

• Donor twin: Blood loss to recipient via AV anastomoses
  • Hypovolemia, oliguria → oligohydramnios ("stuck twin")
  • Growth restriction, anemia
  • Hypotension, reduced placental perfusion
• Recipient twin: Blood volume overload
  • Polyuria → polyhydramnios
  • Hypervolemia, hypertension
  • Cardiac strain → high-output cardiac failure, hydrops
  • Polycythemia (secondary to erythropoietin)

Cardiovascular Consequences:

• Recipient: Cardiomegaly, tricuspid regurgitation, right ventricular dysfunction, hydrops fetalis
• Donor: Hypotension, reduced cardiac output, renal hypoperfusion
• Anaesthetic implications: Recipient twin with cardiac dysfunction may not tolerate labour or uterine contractions

Quintero Staging:

Anaesthetic Considerations in TTTS:

Laser Photocoagulation (Fetoscopic Intervention):

• Often performed under neuraxial anaesthesia or local with sedation
• Risk of preterm labour, rupture of membranes, placental abruption
• Anaesthetic support for maternal comfort and fetal immobilization
• Post-procedure tocolysis and monitoring

Delivery Planning:

• Earlier delivery often required (Stage III-IV)
• Recipient twin may have cardiac decompensation
• NICU team prepared for resuscitation
• Cord blood gas analysis essential

Selective Intrauterine Growth Restriction (sIUGR)

Definition: Discrepant growth in monochorionic twins with estimated fetal weight (EFW) <10th percentile in one twin and <20% discordance.

Types:

• Type I: Positive end-diastolic flow in umbilical artery — better prognosis
• Type II: Persistent absent/reversed end-diastolic flow — high risk of demise
• Type III: Intermittent absent/reversed flow — unpredictable, highest co-twin risk

Anaesthetic Implications:

• Type II/III: High risk of intrauterine fetal demise
• Risk of co-twin exsanguination if demise occurs (acute inter-twin transfusion via AA anastomoses)
• Close fetal monitoring during labour
• Low threshold for operative delivery if fetal distress

Twin Reversed Arterial Perfusion (TRAP) Sequence

Pathophysiology:

• Acardiac twin with no functional heart
• Blood flows retrograde from pump twin to acardiac twin via AA anastomosis
• Pump twin works to perfuse both circulations

Anaesthetic Implications:

• Pump twin cardiac strain, high-output failure risk
• Polyhydramnios common
• May require radiofrequency ablation or occlusion procedure

Clinical Presentation

Preoperative Assessment for Multiple Gestation

History Components:

1. Chorionicity and Zygosity:

• Determined by ultrasound (10-14 weeks optimal)
• Monochorionic = higher risk profile
• Previous TTTS screening and interventions

2. Current Gestation Complications:

• TTTS history or current status (Quintero stage)
• sIUGR type and severity
• Fetal anomalies or anomalies discordance
• Growth discordance percentage
• Polyhydramnios/oligohydramnios
• Fetal wellbeing (biophysical profile, Dopplers)

3. Maternal Medical Conditions:

• Pre-eclampsia (3-5× higher risk in twins)
• Gestational diabetes (higher incidence)
• Anaemia (iron deficiency more common)
• Cardiac disease (greater hemodynamic demands)
• Previous uterine surgery (higher risk with overdistended uterus)

4. Previous Pregnancy History:

• Previous multiple gestation outcomes
• Previous PPH (higher recurrence risk)
• Previous caesarean section (more complex with multiple gestation)

Physical Examination:

Airway Assessment:

• Critical importance: Airway changes more pronounced in multiple gestation (larger uterus, more elevated diaphragm)
• Predictors of difficulty: Mallampati score, thyromental distance, neck mobility, obesity
• Implication: Higher risk of difficult intubation if general anaesthesia required

Cardiovascular:

• Blood pressure: Hypertension screening (pre-eclampsia risk)
• Heart rate: Tachycardia common
• Signs of cardiac decompensation: Dyspnea, orthopnea, peripheral edema
• Auscultation: Flow murmurs common (hyperdynamic circulation)

Respiratory:

• Respiratory rate: May be elevated
• Oxygen saturation: Baseline SpO₂
• Auscultation: Baseline clear, but decompensation possible

Abdominal:

• Fundal height: Greater than dates
• Fetal lie and presentation: Critical for delivery planning
• Scar from previous caesarean section

Investigations:

Essential Laboratory Tests:

• FBC: Haemoglobin (often lower despite higher plasma volume), platelet count (thrombocytopenia risk)
• Coagulation profile: PT, APTT, fibrinogen (baseline, PPH risk assessment)
• Type and screen/crossmatch: Crossmatch 2-4 units blood (higher PPH risk)
• Biochemistry: Renal function, liver function, glucose
• Group and screen: Early crossmatch for potential massive transfusion

Cardiac Evaluation (if indicated):

• Echocardiogram if dyspnea, cardiac history, or signs of decompensation
• ECG baseline

Fetal Assessment:

• Ultrasound: Fetal biometry, presentation, liquor volume, Doppler studies
• Cardiotocography (CTG): Both twins simultaneously (dual CTG monitoring)
• Biophysical profile: Fetal wellbeing assessment

Delivery Planning for Multiple Gestation

Timing of Delivery:

Route of Delivery:

Vaginal Delivery Considerations:

• First twin cephalic, estimated weight >1500 g each
• No other contraindications
• Tertiary centre with immediate OR availability
• Continuous dual CTG monitoring
• Experienced obstetric team
• Anaesthetic team immediately available
• Interval between twins: Ideally <15-30 minutes to reduce risk to second twin

Caesarean Section Indications:

• First twin non-cephalic (breech, transverse)
• Significant growth discordance (>25%)
• Monochorionic monoamniotic (cord entanglement risk)
• Previous uterine scar (relative indication)
• Triplets or higher-order multiples
• Fetal compromise (non-reassuring CTG)
• Maternal request (informed choice)

Management

Anaesthetic Management of Twin Delivery

Neuraxial Anaesthesia for Caesarean Section:

Preferred Technique:

• Spinal anaesthesia: Standard for most elective/urgent twin caesarean sections
• Epidural: If labour epidural in situ, can be topped up
• Combined spinal-epidural (CSE): Flexibility for prolonged surgery or postoperative analgesia

Spinal Dosing Considerations:

• Standard dose: Hyperbaric bupivacaine 0.5% 2.2-2.5 mL (11-12.5 mg)
• Height consideration: Taller patients may need higher end of range
• Obesity: Consider reduced dose (10-11 mg) to reduce block height
• Adjuncts: Fentanyl 10-20 μg, morphine 100-200 μg
• Higher hypotension risk: Due to greater aortocaval compression and blood volume

Positioning:

• Left uterine displacement: 15-30° mandatory (even more critical than singletons)
• Head down tilt: May be required for surgical access with large uterus
• Arm tucking: Ensure arms secured safely for potentially longer surgery

Hemodynamic Management:

Vasopressor Strategy:

• Phenylephrine: First-line (50-100 μg IV bolus, infusion 25-100 μg/min)
  • Preserves uteroplacental perfusion
  • Titrated to maintain SBP within 20% of baseline
• Ephedrine: Reserve for bradycardia or phenylephrine unavailability
  • 5-10 mg IV bolus
  • Avoid in significant uteroplacental insufficiency (reduces uterine blood flow)

Fluid Management:

• Preload: 500-1000 mL crystalloid (limited efficacy)
• Co-load: May be more effective (crystalloid during spinal onset)
• Caution: Avoid fluid overload (higher risk of pulmonary edema in multiple gestation)

Aspiration Prophylaxis:

• Mandatory for all: Higher risk than singletons
• Sodium citrate 0.3 M: 30 mL PO within 30 minutes of surgery
• Ranitidine: 50 mg IV (H2 blocker)
• Metoclopramide: 10 mg IV (prokinetic)
• Consider: Omeprazole 40 mg IV if high aspiration risk

General Anaesthesia for Multiple Gestation:

Indications:

• Category 1 emergency with insufficient time for neuraxial blockade
• Failed neuraxial blockade
• Patient refusal of neuraxial anaesthesia
• Contraindications to neuraxial (coagulopathy, infection)
• Maternal haemodynamic instability

Airway Management:

• Experienced anaesthetist mandatory: Higher difficult airway risk
• Difficult airway cart: Immediately available
• Rapid sequence induction: Thiopental 4-5 mg/kg or propofol 2-3 mg/kg
• Succinylcholine: 1.5 mg/kg (pregnancy dose) or rocuronium 1.2 mg/kg with sugammadex ready
• Sellick maneuver: Until intubation confirmed, position confirmed
• Video laryngoscopy: Consider as first-line (higher success in pregnancy)
• Failed intubation drill: Immediately accessible

Maintenance:

• Volatile agents: 0.5-1.0 MAC until delivery (avoid fetal depression)
• Oxytocin: After both twins delivered (higher dose required)
• Muscle relaxation: Continue until closure complete
• Extubation: Wide awake, full reversal, sitting position

Fetal Monitoring:

• Dual CTG: Continuous monitoring of both twins until delivery
• Paediatric team: Present for each twin
• Cord blood gas: From both cords (important for resuscitation decisions)
• APGAR scores: Recorded separately for each infant

Postpartum Haemorrhage Prevention and Management

Risk Factors in Multiple Gestation:

• Uterine atony (overdistended uterus)
• Large placental bed (more vascular)
• Placental abruption risk
• Higher incidence of placenta praevia/accreta
• Surgical bleeding (caesarean section)

Prophylactic Measures:

• Oxytocin: 5-10 units slow IV bolus after second twin delivered, then 10-40 units in 500 mL crystalloid infusion
  • Higher dose required than singletons (larger uterus)
  • Consider 10 units IM if IV access limited
• Active management of third stage: Controlled cord traction after placental separation
• Uterine massage: After both twins delivered

Uterotonic Escalation (if atony):

Surgical Interventions:

• Uterine compression sutures: B-Lynch or modified techniques
• Bakri balloon: Intrauterine tamponade
• Uterine artery embolization: Interventional radiology (if stable)
• Internal iliac artery ligation: Surgical option
• Hysterectomy: Last resort for uncontrollable bleeding

Blood Product Management:

• Massive transfusion protocol: Activate if >1500 mL blood loss or haemodynamic instability
• Target ratios: 1:1:1 RBC:FFP:Platelets if massive haemorrhage
• Fibrinogen: Maintain >1.5 g/L (cryoprecipitate or fibrinogen concentrate)
• Tranexamic acid: 1 g IV (reduce bleeding, evidence from WOMAN trial)

Vaginal Twin Delivery Anaesthetic Considerations

Epidural Analgesia:

• Recommended: Provides pain relief and rapid conversion to surgical anaesthesia if needed
• Maintenance: Low-dose bupivacaine + fentanyl (patient-controlled epidural analgesia if available)
• Top-up: Prepared for urgent caesarean section if second twin complications

Delivery of Second Twin:

• Interval critical: <15-30 minutes optimal
• Presentation check: Ultrasound or manual assessment after first twin delivered
• External cephalic version: May be required if second twin non-cephalic
• Internal podalic version: Rarely required (breech extraction)
• Breech extraction: Requires adequate analgesia/anaesthesia
• Caesarean section: If second twin distress or malpresentation not correctable

Anaesthetic Options for Second Twin Delivery:

• Epidural top-up: If adequate block and time allows
• Spinal: Rapid onset for urgent second twin delivery
• General anaesthesia: If emergency caesarean section required for second twin

Special Considerations

Selective Fetal Reduction:

• Indications: High-order multiples to reduce to twins, anomalous fetus in multiple gestation
• Anaesthetic: Local with sedation, or neuraxial
• Procedure: Intracardiac potassium chloride (monochorionic: radiofrequency ablation or cord occlusion)
• Risks: Preterm labour, rupture of membranes, infection, miscarriage

Monoamniotic Twins:

• Cord entanglement risk: 50-70% incidence
• Fetal demise risk: 10-20% due to cord accidents
• Delivery: Caesarean section at 32-34 weeks
• Intrapartum: Minimal monitoring interval, immediate delivery capability

Conjoined Twins:

• Incidence: 1:50,000 to 1:100,000 births
• Planning: Extensive multidisciplinary preparation
• Anaesthetic: Complex, prolonged surgery often required
• Neonatal: Shared organs, complex separation or non-separation palliative care

Indigenous Health Considerations

Health Disparities in Multiple Gestation:

Aboriginal and Torres Strait Islander women in Australia experience significant disparities in maternal health outcomes, with these inequities particularly pronounced in high-risk pregnancies including multiple gestations. National perinatal data indicate that Indigenous women have a 1.5-2 times higher rate of multiple pregnancies in some regions, which compounds existing health challenges. The intersection of multiple gestation (inherently higher risk) with socioeconomic determinants creates a multiplier effect on adverse outcomes.

Maternal Mortality and Morbidity:

The maternal mortality ratio for Aboriginal and Torres Strait Islander women remains approximately 3-4 times higher than for non-Indigenous women. In multiple gestation pregnancies, this disparity is even more pronounced due to several intersecting factors. Postpartum haemorrhage (PPH), which occurs at 5-10 times higher rates in multiple gestation regardless of ethnicity, presents a particular risk for Indigenous women who may present with higher rates of anaemia (iron deficiency rates up to 40% in some communities), nutritional deficiencies, and limited access to tertiary-level obstetric care. The risk of severe PPH requiring massive transfusion, interventional radiology, or hysterectomy is significantly elevated in this population.

Access to Care Barriers:

Multiple gestation requires high-risk obstetric monitoring throughout pregnancy, ideally in tertiary centres with maternal-fetal medicine expertise. However, 25-30% of Aboriginal women give birth in rural or remote settings, often without access to the specialized care required for monochorionic twin monitoring, TTTS screening, and delivery planning. The tyranny of distance means that women with multiple gestations in remote communities face the impossible choice of relocating hundreds of kilometres from family and community for months of pregnancy monitoring, or remaining in under-resourced settings with limited specialist care. This geographic isolation disproportionately affects women in the Northern Territory, remote Western Australia, and Queensland, where closure of rural obstetric services has created maternity care deserts.

Culturally Safe Care:

Cultural safety in multiple gestation care requires recognition that Aboriginal women may have different conceptualizations of pregnancy, birth, and family structures. For some communities, multiple births carry specific cultural significance. Traditional birth practices, including connection to Country and involvement of extended family, may be disrupted by the medicalization required in multiple gestation pregnancies (frequent ultrasounds, potential hospitalization for TTTS, planned caesarean delivery). Aboriginal Health Workers (AHWs) and Aboriginal Liaison Officers (ALOs) are essential team members who can bridge cultural understanding, assist with communication, and ensure that medical interventions are explained in culturally appropriate ways. Family decision-making processes, often involving elders and extended kinship networks, differ from individual patient autonomy models and require flexibility in consent processes and care planning.

Systemic Advocacy:

Addressing disparities in multiple gestation outcomes requires systemic change beyond individual patient care. The Closing the Gap initiative must include specific targets for high-risk obstetric care, including access to maternal-fetal medicine services for multiple gestations regardless of geographic location. Telemedicine programs for remote TTTS monitoring, mobile ultrasound services, and culturally appropriate patient transport services are essential infrastructure investments. Additionally, the overrepresentation of Aboriginal women in younger maternal age groups (higher fertility rates) intersects with multiple gestation risks, requiring targeted preconception and early pregnancy health programs. Ensuring that Aboriginal women with multiple gestations receive the same standard of care as non-Indigenous women in urban centres is a matter of reproductive justice and health equity.

ANZCA Exam Focus

ANZCA PS19 (Guidelines for Obstetric Anaesthesia Services)

Key Requirements:

• Multidisciplinary team: Anaesthetic involvement in high-risk antenatal clinics
• 24/7 cover: Consultant anaesthetist available for obstetric emergencies
• Massive transfusion protocol: Activation criteria and availability
• Blood products: Immediate availability for PPH
• Equipment: Difficult airway cart, portable ultrasound
• Documentation: Incident reporting for adverse events

Relevant to Multiple Gestation:

• High-risk pregnancy requiring consultant involvement
• PPH preparation mandatory
• Cell salvage availability for major haemorrhage

OAA Guidelines (Obstetric Anaesthetists' Association)

Labour Ward Anaesthesia Recommendations:

• Epidural availability: 24-hour service for high-risk deliveries
• Epidural top-up: Rapid access for emergency delivery
• General anaesthesia: Equipment and trained personnel immediately available
• Fetal monitoring: Continuous CTG capability

ANZCA Final Examination Topics

Written Examination:

• Pathophysiology of TTTS and implications for anaesthesia
• Haemodynamic changes in multiple gestation
• PPH risk factors and management in twins
• Pharmacology of uterotonics and dosing differences in multiple gestation
• Airway management considerations in the parturient

Clinical Viva:

• Scenario: Monochorionic twins with TTTS requiring caesarean section
• Scenario: Twin delivery with PPH and atony
• Scenario: Failed neuraxial block in twin caesarean section
• Scenario: Second twin distress after vaginal delivery of first twin

Medical Viva:

• Discussion of uteroplacental physiology in multiple gestation
• Cardiovascular adaptations and implications for neuraxial blockade
• Fetal monitoring in labour with multiple gestation
• Postpartum haemorrhage pathophysiology and prevention

Assessment Content

SAQ 1: Twin Caesarean Section with Postpartum Haemorrhage (20 marks)

Scenario: You are the anaesthetic consultant for a 32-year-old woman (G2P1) undergoing elective caesarean section for dichorionic diamniotic twins at 37 weeks gestation. She has a functioning labour epidural in situ (placed 2 hours ago for trial of labour, now proceeding to caesarean section for second twin breech presentation). She received a top-up 30 minutes ago but the block height is inadequate at T10. The obstetric team is ready to proceed urgently. Her vital signs are: BP 110/70 mmHg, HR 92 bpm, SpO₂ 98% on room air. She is anxious but cooperative.

Questions:

1. What are your options for providing anaesthesia for this urgent twin caesarean section? Discuss the advantages and disadvantages of each option. (6 marks)

2. If you proceed with neuraxial anaesthesia, describe your technique and dosing, including specific considerations for multiple gestation. (5 marks)

3. Both twins are delivered successfully, but the uterus is atonic despite oxytocin 10 units IV. Describe your step-by-step management of postpartum haemorrhage in this twin delivery, including uterotonic escalation and blood product management. (6 marks)

4. What are the specific risk factors for PPH in multiple gestation compared to singleton pregnancy, and how does this influence your preparation? (3 marks)

Model Answers:

1. Anaesthetic Options (6 marks):

Option A: Convert Epidural to Surgical Block

• Advantages: Patient awake, avoids GA risks, existing catheter, fetal safety
• Disadvantages: Incomplete block requires supplementation or conversion, takes time (10-15 minutes), uncertain quality
• Technique: Top-up with 15-20 mL 2% lignocaine with 1:200,000 adrenaline, in divided doses, test height

Option B: Single-Shot Spinal

• Advantages: Rapid, reliable, dense block, predictable onset (2-5 minutes)
• Disadvantages: Remove epidural catheter, hypotension risk higher in twins, limited duration (90-120 minutes)
• Dosing: Hyperbaric bupivacaine 0.5% 11-12.5 mg + fentanyl 10-20 μg + morphine 100 μg

Option C: Combined Spinal-Epidural (CSE)

• Advantages: Rapid spinal onset with epidural backup for prolonged surgery or postoperative analgesia
• Disadvantages: More complex, requires additional expertise

Option D: General Anaesthesia

• Advantages: Rapid, reliable, guaranteed conditions
• Disadvantages: Aspiration risk, fetal drug exposure, difficult airway risk, awareness risk, misses neonatal contact

Best Choice: Single-shot spinal (rapid, reliable for urgent delivery) or CSE if expertise available. GA if insufficient time or contraindications to neuraxial.

2. Neuraxial Technique for Twins (5 marks):

Preparation:

• Left uterine displacement mandatory (15-30° left lateral tilt or wedge)
• Fluid preload: 500-1000 mL crystalloid (limited efficacy)
• Aspiration prophylaxis: Sodium citrate 30 mL PO, ranitidine 50 mg IV
• Phenylephrine ready (50-100 μg boluses or infusion 25-100 μg/min)

Spinal Technique:

• L3-L4 or L4-L5 interspace, 25G pencil-point needle
• Hyperbaric bupivacaine 0.5% 11-12.5 mg (higher dose if tall, lower if short/obese)
• Fentanyl 10-20 μg + preservative-free morphine 100-200 μg
• Position supine with left uterine displacement immediately after injection
• Target block height: T4 (test with pinprick or cold sensation)

Hemodynamic Management:

• Phenylephrine first-line (preserves uteroplacental perfusion)
• Avoid ephedrine if uteroplacental insufficiency (reduces uterine blood flow)
• Treat hypotension promptly (SBP <90 mmHg or >20% drop from baseline)

3. PPH Management (6 marks):

Step 1: Call for Help and Activate Protocols (Immediate)

• Call consultant obstetrician, second anaesthetist, theatre team
• Activate massive transfusion protocol if >1500 mL blood loss
• Crossmatch 4-6 units packed red cells, 4 units FFP

Step 2: Optimize Access and Monitoring

• Second large-bore IV (14-16G)
• Arterial line for continuous BP monitoring and serial blood gas
• Foley catheter to monitor urine output

Step 3: Uterotonic Escalation

• Oxytocin infusion: 10-40 units in 500 mL crystalloid at 125 mL/hour (twin dose higher than singleton)
• Ergometrine: 0.25 mg IM if no contraindications (avoid if hypertension or cardiac disease)
• Carboprost: 250 μg IM every 15 minutes (max 2 mg) — avoid if asthma
• Misoprostol: 800-1000 μg PR or SL as adjunct

Step 4: Blood Product Replacement

• Crystalloid: 1-2 L while awaiting blood
• Packed red cells: If Hb <70 g/L or ongoing bleeding, maintain Hb >80 g/L
• FFP: 1:1 ratio with RBC if >4 units RBC transfused or coagulopathy
• Cryoprecipitate: If fibrinogen <1.5 g/L
• Platelets: If <50 × 10⁹/L
• Tranexamic acid: 1 g IV (reduce bleeding, WOMAN trial evidence)

Step 5: Surgical/Interventional (if medical fails)

• Uterine compression sutures (B-Lynch)
• Bakri balloon tamponade
• Uterine artery embolization (interventional radiology)
• Internal iliac artery ligation
• Hysterectomy (last resort)

4. PPH Risk Factors in Twins (3 marks):

Specific Twin Risk Factors:

• Uterine overdistension: Accommodates two fetuses → atomic uterus after delivery
• Larger placental bed: Twice the surface area, more vascular, more bleeding
• Higher caesarean rate: Surgical bleeding contributes
• Higher abruption risk: Particularly in monochorionic pregnancies
• Pre-eclampsia: 3-5× higher incidence → thrombocytopenia, coagulopathy
• Polyhydramnios: TTTS or diabetes → uterine atony

Preparation Implications:

• Crossmatch blood before delivery (2-4 units)
• Large-bore IV access mandatory
• Cell salvage available
• Uterotonic drugs prepared and ready
• Massive transfusion protocol activation criteria established
• Consultant obstetric and anaesthetic presence

SAQ 2: TTTS Laser Photocoagulation Anaesthetic Management (20 marks)

Scenario: A 28-year-old woman at 22 weeks gestation with monochorionic diamniotic twins has been diagnosed with Quintero Stage II twin-to-twin transfusion syndrome (oligo-poly sequence with absent donor bladder). She is scheduled for fetoscopic laser photocoagulation of placental anastomoses. She is anxious and requests information about the procedure and anaesthetic options.

Questions:

1. Explain the pathophysiology of TTTS and why this patient requires intervention. (5 marks)

2. Describe the anaesthetic options for fetoscopic laser photocoagulation, including advantages and disadvantages of each. (6 marks)

3. What are the intraoperative and postoperative anaesthetic considerations and potential complications for this procedure? (5 marks)

4. If the laser procedure fails and the recipient twin develops hydrops fetalis requiring delivery at 28 weeks, describe the anaesthetic management considerations for this extremely preterm twin delivery. (4 marks)

Model Answers:

1. TTTS Pathophysiology (5 marks):

Mechanism:

• Monochorionic placenta with unbalanced arteriovenous anastomoses
• Net blood flow from donor to recipient via deep AV anastomoses
• Insufficient compensatory arterio-arterial anastomoses

Pathophysiological Sequence:

• Donor twin: Hypovolemia → decreased renal perfusion → oliguria → oligohydramnios ("stuck twin" in cramped sac)
• Recipient twin: Hypervolemia → polyuria → polyhydramnios → cardiac volume overload

Cardiac Consequences:

• Recipient: High-output cardiac failure, cardiomegaly, tricuspid regurgitation, right ventricular dysfunction, hydrops (pericardial/pleural effusions, ascites, skin edema)
• Donor: Growth restriction, anemia, hypoperfusion

Quintero Stage II:

• Oligo-poly sequence present
• Absent donor bladder (significant oliguria)
• Intervention indicated to prevent progression to Stage III-IV with cardiac failure
• Laser photocoagulation interrupts anastomoses, equalizes circulations

Untreated Prognosis:

• 80-90% mortality if untreated (both twins)
• High morbidity in survivors (cardiac, neurological)

2. Anaesthetic Options (6 marks):

Option A: Local Anaesthesia with Sedation

• Technique: Local infiltration at trocar insertion sites + IV sedation (low-dose propofol infusion or midazolam/fentanyl)
• Advantages: Minimal fetal drug exposure, mother awake, rapid recovery, fetal movement may be tolerated
• Disadvantages: Patient discomfort with uterine manipulation, limited duration if prolonged, maternal movement risk, may need conversion
• Monitoring: Standard obstetric monitoring, fetal heart rate

Option B: Neuraxial Anaesthesia (Spinal or Epidural)

• Technique: Spinal (bupivacaine 7.5-10 mg) or epidural (10-15 mL 2% lignocaine with adrenaline)
• Advantages: Complete maternal comfort, immobile patient, better surgical conditions, can extend duration with epidural
• Disadvantages: Hypotension risk (reduces uteroplacental perfusion), longer recovery, fetal drug exposure minimal but present, post-dural puncture headache risk
• Hemodynamic: Phenylephrine to maintain BP, left uterine displacement

Option C: General Anaesthesia

• Indications: Rarely used, only if neuraxial contraindicated or patient preference after counseling
• Advantages: Guaranteed immobility, airway protected (RSI), controlled conditions
• Disadvantages: Fetal drug exposure (volatile agents cross placenta), airway risk, aspiration risk, longer recovery, potential for uterine relaxation with volatiles

Optimal Choice:

• Local with sedation for straightforward cases
• Neuraxial for anxious patients, expected prolonged procedure, or if uterine manipulation significant
• GA rarely indicated

3. Intraoperative and Postoperative Considerations (5 marks):

Intraoperative Considerations:

Patient Positioning:

• Supine with left uterine displacement (even at 22 weeks, uterus compresses IVC)
• Trendelenburg or lateral tilt may be needed for surgical access
• Pressure points protected (prolonged procedure)

Fetal Monitoring:

• Continuous fetal heart rate monitoring of both twins
• Fetal immobilization may be required (maternal positioning, paralytic crossing placenta if GA used)
• Cord Doppler assessment before and after laser

Tocolysis:

• Atosiban or nifedipine typically given prophylactically to prevent preterm labour
• Monitor for uterine contractions

Complications:

• Preterm rupture of membranes: 10-20% risk
• Preterm labour: 10-15% risk
• Placental abruption: Rare but catastrophic
• Bleeding: Maternal or fetal (rare)
• Laser failure: May need repeat procedure

Postoperative Considerations:

Monitoring:

• Fetal heart rate monitoring (both twins)
• Ultrasound assessment of amniotic fluid volumes (both sacs)
• Doppler studies (end-diastolic flow, ductus venosus)
• Tocolysis continued

Analgesia:

• Simple analgesia (paracetamol, NSAIDs if not contraindicated)
• Opioids if epidural not used
• Monitor for preterm labour pain vs. surgical pain

Follow-up:

• Serial ultrasounds to assess TTTS resolution
• Monitor for fetal demise (donor or recipient)
• Delivery planning based on response

4. Preterm Twin Delivery at 28 Weeks (4 marks):

Maternal Anaesthetic Considerations:

• Neuraxial preferred: If time allows and no contraindications (spinal or CSE)
• Left uterine displacement: Critical
• Hypotension management: Phenylephrine preserves uteroplacental perfusion
• Aspiration prophylaxis: Mandatory
• Temperature management: Prevent hypothermia (preterm neonate resuscitation)

Neonatal Resuscitation:

• Neonatal team: Experienced team for 28-weekers
• Equipment: Prepared for extremely preterm infants (incubator, surfactant, ventilator)
• Cord clamping: Delayed cord clamping if feasible (benefits for preterm)
• Cord blood gas: Essential for both twins

PPH Prophylaxis:

• Higher risk due to preterm uterus and twin overdistension
• Active management of third stage
• Blood products available

Postoperative:

• ICU or high-dependency bed may be needed
• Corticosteroids for fetal lung maturity should have been given antenatally
• Lactation support if desired (preterm infants require expressed breast milk)

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